U.S. patent number 7,981,280 [Application Number 11/443,699] was granted by the patent office on 2011-07-19 for recirculation of blood in an extracorporeal blood treatment system.
This patent grant is currently assigned to Renal Solutions, Inc.. Invention is credited to Stephen R. Ash, David J. Carr.
United States Patent |
7,981,280 |
Carr , et al. |
July 19, 2011 |
Recirculation of blood in an extracorporeal blood treatment
system
Abstract
An extracorporeal blood treatment apparatus includes a blood
treatment unit, a treatment fluid circuit, and a blood circuit. The
treatment fluid circuit has a treatment fluid pump for circulating
treatment fluid around the treatment fluid circuit and through the
blood treatment unit. The blood circuit has a dual chamber blood
pump for circulating blood around the blood circuit and through the
blood treatment unit. An arterial line withdraws blood from a
patient and delivers the withdrawn blood to the blood treatment
unit. A venous line returns the treated blood to the patient. The
arterial and venous lines can be switched between a first condition
in which they are connected to the patient and a second condition
in which they are disconnected from the patient and connected to
each other for recirculation of blood through the blood circuit. A
controller operates the blood pump, and switches the blood pump
between a condition in which the dual chambers operate in phase
with each other and a condition in which the dual chambers operate
out of phase with each other.
Inventors: |
Carr; David J. (West Lafayette,
IN), Ash; Stephen R. (Lafayette, IN) |
Assignee: |
Renal Solutions, Inc.
(Warrendale, PA)
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Family
ID: |
38231727 |
Appl.
No.: |
11/443,699 |
Filed: |
May 31, 2006 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20070158247 A1 |
Jul 12, 2007 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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60756782 |
Jan 6, 2006 |
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Current U.S.
Class: |
210/134; 210/252;
210/96.2; 210/194; 210/141; 604/6.11; 210/143; 604/6.09; 604/66;
210/85; 210/195.2; 604/67; 604/65 |
Current CPC
Class: |
A61M
1/3603 (20140204); A61M 1/3431 (20140204); A61M
1/16 (20130101); A61M 60/40 (20210101); A61M
60/268 (20210101); A61M 60/869 (20210101); A61M
60/113 (20210101); A61M 2205/18 (20130101) |
Current International
Class: |
B01D
61/28 (20060101); B01D 61/32 (20060101); B01D
61/00 (20060101) |
Field of
Search: |
;210/85,96.2,134,141,143,194,195.2,252 ;604/6.09,6.11,65,66,67 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Kim; John
Attorney, Agent or Firm: Fish & Richardson P.C.
Parent Case Text
RELATED APPLICATIONS
This application claims the benefit of Provisional Application Ser.
No. 60/756,782, filed Jan. 6, 2006, which is incorporated by
reference.
Claims
What is claimed is:
1. An extracorporeal blood treatment apparatus comprising: a blood
treatment unit; a treatment fluid circuit including a treatment
fluid pump operative to circulate treatment fluid around the
treatment fluid circuit and through the blood treatment unit; a
blood circuit including a blood pump operative to circulate blood
around the blood circuit and through the blood treatment unit, an
arterial line for withdrawing blood from a patient, and a venous
line for returning the treated blood to the patient, the blood pump
comprising two chambers and the arterial and venous lines being
configured to be switched between a first condition in which they
are connected to the patient and a second condition in which they
are disconnected from the patient and connected to each other for
recirculation of blood through the blood circuit; and a controller
configured to operate the pumps in a treatment mode during which
both the blood pump and the treatment fluid pump are operated to
circulate blood and treatment fluid through the blood treatment
unit while the arterial and venous lines are in the first
condition, and in a recirculation mode during which the treatment
fluid pump is inactivated and the blood pump is operated to
circulate the blood through the blood circuit while the arterial
and venous lines are in the second condition.
2. The apparatus of claim 1 wherein the controller is configured to
switch the blood pump between a condition in which the dual
chambers operate in phase with each other and a condition in which
the dual chambers operate out of phase with each other.
3. The apparatus of claim 2 wherein the controller is further
configured to operate the blood pump such that the dual chambers
are out of phase during the recirculation mode.
4. The apparatus of claim 1 further comprising an input device
coupled to the controller and operative to allow an operator to
input a command to the controller to initiate the recirculation
mode.
5. The apparatus of claim 1 further comprising an input device
coupled to the controller and operative to allow an operator to end
the recirculation mode.
6. The apparatus of claim 1 further comprising a bubble detector
and an input device coupled to the controller and operative to
alert an operator when the bubble detector detects a bubble in the
blood circuit and operative to allow the operator to input a
command to the controller to initiate the recirculation mode.
7. The apparatus of claim 1 further comprising a bubble detector
and wherein the controller is further configured to continue the
recirculation mode until the bubble detector does not detect a
bubble in the blood circuit for a predetermined number of cycles of
recirculation.
8. The apparatus of claim 1 wherein the controller is configured to
display instructions for switching the arterial and venous lines
from their first condition to their second condition after the
recirculation mode is initiated.
9. The apparatus of claim 1 wherein the controller is configured to
pause the blood pump when recirculation is initiated to allow time
for switching the arterial and venous lines from their first
condition to their second condition.
10. The apparatus of claim 8 wherein the controller is further
configured to prompt the operator to end treatment when the blood
pump has been paused for a predetermined amount of time x.
11. The apparatus of claim 9 wherein the controller is configured
to display a countdown time remaining to the end of time x.
12. The apparatus of claim 9 wherein the controller is configured
to sound an alarm before the end of time x.
13. The apparatus of claim 1 wherein the controller is configured
to prompt the operator to end treatment when the recirculation mode
has been operating for a predetermined amount of time y.
14. The apparatus of claim 13 wherein the controller is configured
to display a countdown time remaining to the end of time y.
15. The apparatus of claim 13 wherein the controller is configured
to sound an alarm before the end of time y.
16. The apparatus of claim 1 wherein the blood treatment unit is a
dialyzer.
Description
FIELD
This invention relates to systems and methods for the
extracorporeal treatment of blood.
BACKGROUND
A dialysis system is used as a substitute for the natural kidney
function of a human body. The dialysis system cleans the blood of
the natural accumulation of bodily wastes by separating the wastes
from the blood in an extracorporeal blood treatment apparatus. The
separated wastes are discharged and the cleansed blood is returned
to the body.
The dialysis system includes a blood tubing set, a dialysate tubing
set, a dialysate fluid, and a dialyzer where the processing of
blood takes place. Typically, a dialyzer includes a semi-permeable
membrane located within a closed housing which effectively
separates the housing into a blood compartment and a dialysate
compartment. The blood removed from the patient flows through the
blood circuit and enters the blood side of the dialyzer. The
dialysate solution is passed through the dialysate side of the
dialyzer. The waste from the blood passes through the membrane into
the dialysate fluid.
SUMMARY
An extracorporeal blood treatment apparatus includes a blood
treatment unit, a treatment fluid circuit and a blood circuit. The
treatment fluid circuit has a treatment fluid pump for circulating
treatment fluid around the treatment fluid circuit and through the
blood treatment unit. The blood circuit has a dual chamber blood
pump for circulating blood around the blood circuit and through the
blood treatment unit. An arterial line withdraws blood from a
patient and delivers the withdrawn blood to the blood treatment
unit. A venous line returns the treated blood to the patient. The
arterial and venous lines can be switched between a first condition
in which they are connected to the patient and a second condition
in which they are disconnected from the patient and connected to
each other for recirculation of blood through the blood
circuit.
The apparatus also includes a controller that operates the
treatment fluid pump and the blood pump in a plurality of modes,
including a treatment mode and a recirculation mode. In the
treatment mode, both the blood pump and the treatment fluid pump
are operated to circulate blood and treatment fluid through the
blood treatment unit while the arterial and venous lines are in the
first condition. In the recirculation mode, the treatment fluid
pump is inactivated, and the blood pump is operated to circulate
the blood through the blood circuit while the arterial and venous
lines are in their second condition. The controller is further
configured to switch the blood pump between a condition in which
the dual chambers operate in phase with each other and a condition
in which the dual chambers operate out of phase with each
other.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic view of an extracorporeal blood treatment
system.
FIG. 1A is a schematic view of part of the system of FIG. 1.
FIG. 2 is a schematic view of a patient connected to the arterial
and venous lines of the system in FIG. 1.
FIG. 3 is another schematic view of a patient connected to the
arterial and venous lines of the system in FIG. 1.
FIG. 4 is a schematic view of the arterial and venous lines of the
system in FIG. 1 connected to each other.
FIG. 5 is a flow chart representing the steps involved in
recirculation of blood in the system of FIG. 1.
FIGS. 6-12 are examples of display screens and their user interface
areas for the system in FIG. 1.
DESCRIPTION
The dialysis systems shown schematically in the drawings have parts
that are examples of the elements recited in the apparatus claims,
and can be operated in steps that are examples of the elements
recited in the method claims. The illustrated systems thus include
examples of how a person of ordinary skill in the art can make and
use the claimed invention. They are described here to meet the
enablement and best mode requirements of the patent statute without
imposing limitations that are not recited in the claims.
The apparatus 10 shown in FIG. 1 is a renal dialysis system for the
extracorporeal treatment of blood from a patient whose kidney
function is impaired. The dialysis system comprises a blood circuit
12 through which the patient's blood travels, a dialyzer 13 that
serves to separate the wastes from the blood, and a dialysate
circuit 14 through which treatment fluid, specifically dialysate,
travels carrying the waste away. The claims define an apparatus and
method of recirculating blood through a blood treatment system such
as the dialysis system shown in FIG. 1.
The dialysate circuit 14 includes a dialysate pump 15 for driving
dialysate fluid around the dialysate circuit 14 and through the
dialyzer 13. The dialysate circuit 14 may further include other
components such as those described in U.S. patent application Ser.
No. 11/148,928, entitled Dialysis System and filed on Jun. 9, 2005,
which is hereby incorporated by reference.
The dialyzer 13 is a known device that contains a semi-permeable
membrane 16 that separates a blood compartment 17 from a dialysate
fluid compartment 18. The dialyzer 13 operates such that blood
flows in one direction through the blood compartment 17 while
dialysate fluid flows in the opposite direction through the
dialysate compartment 18. In this way, urea and other small blood
impurities pass through the membrane 16 from the blood side 17 to
the dialysate side 18, but blood cells and other blood components
which are too large to pass through the membrane 16 are retained in
the blood.
The blood circuit 12 includes an arterial line 20 for withdrawing
blood from a patient and delivering it to the dialyzer 13, and a
venous line 24 for returning the treated blood to the patient. A
blood pump 26 drives the blood around the circuit. The arterial
line 20 incorporates a valve 30 that can stop the flow of blood
from the patient, an air detector 32 that can detect air in the
arterial line 20, and a flow sensor 34 that measures the flow of
blood.
The blood pump 25 in the illustrated example is configured as
described in U.S. patent application Ser. No. 10/399,128, entitled
Device and Methods for Body Fluid Flow Control In Extracorporeal
Fluid Treatments, filed Jul. 28, 2003, which is incorporated by
reference. As shown schematically in FIG. 1A, the blood pump 26
thus includes a dual chamber device 36 and a source of pneumatic
pressure 38. The dual chamber device 36 defines two chambers 39
that can be arranged in parallel, as shown in FIG. 1A, or in
series, as shown in application Ser. No. 10/399,128. The two
chambers 39 contain two flexible membranes 40. Each flexible
membrane 40 divides a corresponding chamber 39 into first and
second pumping chambers 41 and 43. A pair of arterial branch lines
44 with inlet and outlet valves 46 and 48 communicate the arterial
line 20 with inlet and outlet ports 50 and 52 at the first pumping
chambers 41. Gaseous ports 54 at the second pumping chambers 43
communicate with the source of pneumatic pressure 38 through
pneumatic lines 56 and a directional valve 58.
The various parts of the blood pump 26 cooperate to pump blood
through the venous line 20 in the direction indicated by the arrows
shown in FIG. 1A. When the directional control valve 58 directs
negative pneumatic pressure to either of the second pumping
chambers 43, the adjacent flexible membrane 40 deflects to enlarge
the first pumping chamber 41 and thereby to draw blood into the
first pumping chamber 41. When the directional control valve 58
subsequently directs positive pneumatic pressure to the second
pumping chamber 43, the flexible membrane 40 deflects back to
constrict the first pumping chamber 41 and thereby to expel blood
from the first pumping chamber 41. The inlet and outlet valves 46
and 48 are opened and closed accordingly. The dual chambers 39 are
both operated in this manner to pump blood through the two branch
lines 44.
The directional control valve 58 can provide the two gaseous ports
54 with positive pneumatic pressure at the same time, and with
negative pneumatic pressure at the same time. The dual chambers 39
then move blood fully in phase with each other. If the directional
control valve 58 provides the gaseous ports 54 with positive and
negative pressures alternatively rather than simultaneously, the
dual chambers 39 will move blood fully or partially out of phase
with each other, depending on the degree to which the positive and
negative pressures are out of phase with each other. Importantly,
when the dual chambers 39 expel blood out of phase, each chamber 39
acts as a compliant chamber for the other by receiving a volume of
blood corresponding to the degree to which the two chambers 39 are
out of phase. This can be an advantage in use of the recirculation
mode of the claimed invention, as described more fully below.
Other components of the blood circuit 12 include a source of fluid,
such as a saline bag 60, which communicates with the arterial line
20 via a branch line 62 and a valve 64. Additionally, an
anticoagulant solution such as a heparin supply 65 may communicate
with the arterial line 20 through a branch line 67 and a pump 68.
It is understood by persons skilled in the art that additional
elements may be added to the blood circuit 12, such as air
detectors in the branch lines 62 or 67. These additional elements
are omitted from the drawings for clarity of illustration. Finally,
the venous line 24 delivers the treated blood from the dialyzer 13
to the patient and also includes a valve 70, an air detector 72 and
a flow sensor 74.
The arterial and venous lines 20 and 24 can be coupled to the
patient via separate patient connectors 80 and 82, as depicted in
FIG. 2. The arterial line 20 also includes a manual clamp 83 and a
connector 84. Similarly, the venous line 24 includes a manual clamp
85 and a connector 86. Alternatively, the arterial and venous lines
20 and 24 may be connected to the patient via a dual access
connector 90 and a patient connector 91, which can be a needle or a
catheter, as depicted in FIG. 3. Again, manual clamps 93, 95 and
connectors 96, 98 are provided on the arterial and venous lines 20
and 24 respectively. In either case, the arterial and venous lines
20 and 24 can be disconnected from the patient by closing the
manual clamps 83, 85 in the case of two connectors, or 93, 95 in
the case of a dual access connector 90. The arterial and venous
lines 20 and 24 may then be separated from the patient at the
connectors 84, 86 or 96, 98 and connected together via an
inter-connector 99, as depicted in FIG. 4.
A controller 100 coordinates the operation of the dialysis system
10 by controlling the blood flow in the blood circuit 12, the
dialysate flow in the dialysate circuit 14, and the flow of saline
or heparin to the arterial line 20 via the branch lines 62 and 67.
To achieve this, the controller 100 utilizes hardware and/or
software configured for operation of these components and may
comprise any suitable programmable logic controller or other
control device, or combination of control devices, that is
programmed or otherwise configured to perform as recited in the
claims. Thus, blood flow in the blood circuit 12 is controlled by
operating the blood pump 26 and controlling the valves 30 and 70 in
the arterial and venous lines 20 and 24. Dialysate flow in the
dialysate circuit 14 is controlled by operating the dialysate pump
15.
The controller 100 is also responsive to various input signals it
receives, such as input signals from one or more flow sensors 34
and 74 and air detectors 32 and 72. Additionally, the controller
100 displays system status and various other treatment parameters,
known in the art, on a display screen that allows the operator to
interact with the controller 100 via an operator interface. The
operator interface of the display screen may be in the form of a
series of buttons, a touch sensitive control screen, or any other
means that allow an operator to interact with the controller
100.
Having detailed the various components of the dialysis system 10,
now follows a description of how the various parts function to
effect recirculation of blood within the blood circuit 12.
The controller 100 has at least two modes of operation. One is a
standard dialysis treatment mode during which blood is withdrawn
from the patient, pushed through the blood circuit 12 in the
direction indicated by arrow 182, and delivered back to the patient
while dialysate solution is circulated through the dialysate
circuit 14 and dialyzer 13 in the direction indicated by arrow 184.
During this mode, the valves 30 and 70 in the arterial and venous
lines 20 and 24 are kept open to effect the withdrawal and delivery
of blood to the patient. The driving force of the positive and
negative pneumatic pressures at the blood pump 26 are determined by
the controller 100 in response to the blood flow rates sensed by
the flow sensors 34 and 74. During this standard dialysis treatment
mode, saline or heparin may be delivered to the arterial line 20
via the corresponding branch lines 62 and 67. The dialysate pump 15
drives the dialysate solution around the dialysate circuit 14 and
is activated by the controller 100 in response to a set of
preprogrammed parameters and inputs such as the dialysate flow rate
and other input signals known in the art that may take part in the
performance of a dialysis treatment on a patient.
A second mode preprogrammed into the controller 100 is the
recirculation function during which blood circulates in the blood
circuit 12 in a closed loop bypassing the patient while dialysate
fluid circulation is paused. The recirculation mode can be used in
at least two instances; when a patient needs to temporarily
disconnect from the dialysis system 10, or when air is detected in
the blood circuit 12. In either case, an operator, who may be the
patient, can interact with the controller 100 to initiate the
recirculation mode. The steps for the recirculation mode are
outlined in FIG. 5.
When a patient needs to temporarily disconnect from the dialysis
system 10, the operator may pause treatment by interacting with the
controller 100. This selection prompts the controller 100 to pause
the blood pump 26, pause the dialysate pump 15, close the valves 30
and 70 adjacent to the patient, and display a "Treatment Paused"
screen 200, such as the one depicted in FIG. 6. The operator then
selects "Recirculate" on the operator interface of the controller
100, in this example the display screen 200. In response, the
controller 100 displays a "Recirculation Setup" screen 300, such as
the one depicted in FIG. 7. The operator is allowed a predetermined
amount of time x to prepare for recirculation by disconnecting the
arterial and venous lines 20 and 24 from the patient and connecting
the two lines together. The recirculation setup screen 300 alerts
the operator that treatment has been paused and displays a
countdown clock 303 which indicates the length of time the operator
has to prepare for recirculation. The setup screen 300 also
provides instructions for the steps the operator must take to
prepare for recirculation. These steps include (i) closing the
manual clamps 83, 85 or 93, 95; (ii) separating the arterial and
venous lines 20 and 24 from the patient at the connectors 84, 86 or
96, 98; and (iii) connecting the arterial and venous lines 20 and
24 together via the interconnector 99 to form a closed loop.
While the controller 100 displays the recirculation setup screen
300, the blood pump 26 can be stopped for a maximum time x. This
avoids coagulation that might otherwise occur if the blood were
permitted to remain stationary in the blood circuit 12 for a longer
period. Time x is predetermined on the basis of clinical and
practical considerations, and is preprogrammed into the controller
100. In this example, time x is five minutes. Time x, however, may
have a different value as long as the value will ensure that the
standing blood does coagulate. To ensure that the operator is aware
of the passage of time x, the controller 100 will display a
countdown clock, as described above, and will sound an alarm
periodically such as every minute. If during time x the operator
fails to cancel the recirculation selection or fails to disconnect
the patient and start recirculation, the controller 100 sounds a
different alarm and displays a screen alerting the operator that
treatment must end.
If the steps for disconnecting the patient have been performed
successfully during the allowed time x, the operator can interact
with the setup screen 300 to begin recirculation, e.g. by pressing
the "Begin" button on the setup screen 300. At this prompt, the
controller 100 displays a "Confirm Recirculation" screen 400. If
the operator disconfirms by pressing "No", the controller 100
reverts back to displaying the recirculation setup screen 300. If
the operator confirms preparation by pressing "Yes," the controller
100 starts recirculation of blood by reactivating the blood pump 26
and reopening the valves 30 and 70 adjacent to the patient while
the dialysate pump 15 remains inactive. The controller 100 then
resumes blood flow in the direction of the arrow 182. Preferably,
the controller 100 operates the blood pump 26 with the two chambers
39 in phase during the standard dialysis treatment mode, and
switches the blood pump 26 to a condition in which the two chambers
39 operate out of phase, and preferably fully or 180.degree. out of
phase, in the recirculation mode. Compared with in-phase operation
of the dual chambers 39, the compliant chamber in out-of-phase
operation provides volume needed for the blood to flow through the
closed loop of the blood circuit 12 during recirculation. The
controller 100 alerts the operator that recirculation is in
progress by displaying a "Recirculation In Progress" screen 500,
such as the one depicted in FIG. 9.
Recirculation may proceed for only a predetermined amount of time
y. The screen 500 alerts the operator as to when recirculation must
end by displaying a countdown clock. During the last few minutes of
the countdown, an alarm will sound prompting the operator to
reconnect to the dialysis system 10 and to run the system in the
normal dialysis treatment mode. As with time x, the controller 100
is programmed with a predetermined time y. In this example, time y
is 20 minutes and the alarm is set to sound periodically during the
last five minutes. These times, however, may have different values
as long as the values will ensure that the recirculating blood does
not coagulate. If the operator fails to reconnect the patient and
resume treatment at the end of time y, the controller 100 displays
a screen alerting the operator that recirculation must end.
The operator is also not able to stop recirculation unless the
controller 100 detects no air in the arterial and venous lines 20
and 24 for a number z of uninterrupted blood cycles. Thus,
initially, on the display screen 500, the "End Recirculation"
button is not enabled. Once the air detectors 32 and 72 do not
detect air the number z of cycles, the controller 100 displays a
screen 600, such that depicted in FIG. 10, where the "End
Recirculation" button is enabled. The number z also has a
predetermined valve in the controller 100 which, in this example,
is 2 cycles.
During the allowed time y and while screen 600 is displayed, the
operator can interact with the operator interface to end
recirculation by pressing the enabled "End Recirculation" button.
At this command, the controller 100 stops the flow of blood by
pausing the blood pump 26 and closing the valves 30 and 70. The
controller 100 then displays a "Reconnect Patient Access" screen
700, such as the screen depicted in FIG. 11, which alerts the
operator that recirculation has stopped, shows the predetermined
time x during which the operator must reconnect the patient to the
dialysis system 10, and displays instructions for reconnecting the
patient. Once the patient has been reconnected to the dialysis
system 10, the operator can interact with the operator interface,
e.g. by pressing the "Completed" button on screen 700. The
controller 100 then restarts blood flow through the blood circuit
12 by opening the valves 30 and 70 and restarting the blood pump
26, preferably with in-phase operation of the dual chambers 39. The
controller 100 also restarts dialysate fluid flow through the
dialysate circuit 14 by reactivating the dialysate pump 15. In this
manner, normal treatment and molecular exchange between the blood
and dialysate fluid is resumed in the dialyzer 13. Operation of the
saline valve 64, which is preferably maintained in a closed
condition throughout the recirculation mode to block blood from
entering the saline reservoir 60, can likewise be resumed as needed
during the treatment mode.
The controller 100 can also prompt an operator to start the process
of recirculating blood when air is detected by the air detectors 32
or 72. When air is detected in the blood circuit 12, the controller
pauses the blood pump 26 and the dialysate pump 15, sounds an alarm
and displays an "Air Detected" screen 800, such as the one shown in
FIG. 12. This screen alerts the operator that air has been detected
and displays a "Recirculate" button that allows the operator to
initiate blood recirculation. When the operator selects
"Recirculate," the controller 100 will display the "Recirculation
Setup" screen 300 and the operator and controller 100 can interact,
following the same steps as described previously, to effect
recirculation of blood. As mentioned above, the operator is not
able to stop recirculation unless the blood has completed a
predetermined number z of uninterrupted cycles around the blood
circuit 12 without the detectors detecting air. This ensures that
the blood circuit 12 has been purged of air before dialysis can be
resumed. Recirculating blood through the blood circuit 12, and
though the dialyzer 13, removes air from the blood as the air
becomes trapped in the top portion of the dialyzer 13. However, it
may be preferable to drive air upward into the saline bag 60. The
controller 100 can accomplish this by holding the saline valve 62
open, and by operating the blood pump 26 with the dual chambers 39
in phase with each other (and preferably fully in phase with each
other) so that the closed blood recirculation circuit 12 does not
obtain the volume of a compliant chamber 39. In the absence of a
compliant chamber 39 at the blood pump 26, the saline bag 60 will
provide the volume needed to capture air from the closed circuit
12.
As previously, if the blood pump 26 is paused for longer than the
allowed time x, e.g. because the operator failed to initiate
recirculation while the "Air Detected" screen 800 is displayed, the
controller 100 will again sound an alarm and alert the operator
that treatment must end. To ensure that the operator is aware of
this time limitation, the "Air Detected" screen 800 displays a
count down clock and clearly states that the operator must either
clear the alarm (by initiating recirculation) or end treatment by
the end of the counted down time.
This written description sets forth the best mode of the invention,
and describes the invention so as to enable a person skilled in the
art to make and use the invention, by presenting examples of the
elements recited in the claims. The patentable scope of the
invention is defined by the claims, and may include other examples
that occur to those skilled in the art. Such other examples, which
may be available either before or after the application filing
date, are intended to be within the scope of the claims if they
have elements that do not differ from the literal language of the
claims, or if they have equivalent elements with insubstantial
differences from the literal language of the claims.
* * * * *